The Washington meridians are four meridians that were used as prime meridians in the United States and pass through Washington, D.C.. The four which have been specified are:
- through the Capitol
- through the White House
- through the old Naval Observatory
- through the new Naval Observatory.
Their longitudes may be reported in three ways:
- relative to the local vertical used by astronomic observations
- relative to NAD 27 (North American Datum 1927), an ellipsoid of revolution that is at mean sea level beneath triangulation station Meades Ranch, Kansas (not earth-centered);
- relative to NAD 83, an earth-centered ellipsoid of revolution with dimensions chosen to best fit the undulating (±100 m) geoid (world-wide mean sea level).
NAD83 longitude of the Capitol is about 1.1 arc seconds less than its NAD27 longitude; astronomic longitude there is about 4 arc seconds less than NAD83.
Other articles related to "washington meridian, meridian, washington":
... The fourth meridian was through the clock room of the new Naval Observatory, 2.3 miles (3.8 km) northwest of the White House, at 77°3'56.7"W (1897) or 77°4 ... variable of time for a few tables (even though Washington's civil time since 1883 had been that of the standard time zone GMT−5 hours (75°W)) ...
... Washington Mean Time was the time at the meridian through the center of the old dome atop the main building at the old US Naval Observatory at Washington, D.C ... This Washington meridian was defined on 28 September 1850 by the United States Congress ... Washington Mean Time was sometimes called Washington Meridian Time ...
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